U.S. patent number 6,247,914 [Application Number 08/849,837] was granted by the patent office on 2001-06-19 for casing material and a method and apparatus for its manufacture.
This patent grant is currently assigned to SCA Hygiene Products AB. Invention is credited to Stefan Areskoug, Bengt Lindquist, Anders Str.ang.lin.
United States Patent |
6,247,914 |
Lindquist , et al. |
June 19, 2001 |
Casing material and a method and apparatus for its manufacture
Abstract
The invention relates to a method and to an apparatus for
perforating a web of material intended to form an outer casing
sheet of absorbent articles. As the web is advanced, the web is
first provided with a large number of mutually separated cuts in
the nip defined between raised plateaus on a matrix cylinder and
circumferentially extending knife-edges of a cutting cylinder. The
web is then deformed transversely to its plane at parts which
border on each cut. The invention also relates to a perforated
outer casing sheet which includes recesses in the form of mutually
adjacent elongated channel-like grooves.
Inventors: |
Lindquist; Bengt (Lerum,
SE), Areskoug; Stefan (Molnlycke, SE),
Str.ang.lin; Anders (Torslanda, SE) |
Assignee: |
SCA Hygiene Products AB
(Gothenburg, SE)
|
Family
ID: |
20396532 |
Appl.
No.: |
08/849,837 |
Filed: |
June 30, 1997 |
PCT
Filed: |
December 28, 1995 |
PCT No.: |
PCT/SE95/01594 |
371
Date: |
June 30, 1997 |
102(e)
Date: |
June 30, 1997 |
PCT
Pub. No.: |
WO96/20673 |
PCT
Pub. Date: |
July 11, 1996 |
Foreign Application Priority Data
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|
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Dec 30, 1994 [SE] |
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9404579 |
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Current U.S.
Class: |
425/294; 264/145;
264/146; 264/154; 264/155; 264/156; 264/284; 425/298; 425/304;
425/362; 425/363; 425/80.1; 425/81.1; 425/82.1; 425/83.1; 428/132;
428/133; 493/365; 493/370; 604/385.01 |
Current CPC
Class: |
B26F
1/20 (20130101); B29D 7/01 (20130101); B26F
1/18 (20130101); Y10T 428/24289 (20150115); Y10T
428/24281 (20150115) |
Current International
Class: |
B26F
1/00 (20060101); B26F 1/18 (20060101); B26F
1/20 (20060101); B29D 7/00 (20060101); B29D
7/01 (20060101); B28B 059/04 (); B29C 011/12 () |
Field of
Search: |
;428/132,133
;425/80.1,81.1,82.1,83.1,294,298,304,362,363
;264/145,146,154,155,156,284 ;604/385.01 ;493/365,370 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 195 113A2 |
|
Sep 1986 |
|
EP |
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0 301 599 A2 |
|
Feb 1989 |
|
EP |
|
7-178697 |
|
Jul 1995 |
|
JP |
|
176551 |
|
Apr 1995 |
|
PL |
|
Primary Examiner: Watkins, III; William P.
Attorney, Agent or Firm: Burns, Doane, Swecker & Mathis,
L.L.P.
Claims
What is claimed is:
1. Apparatus for perforating a web of material intended to form an
outer casing sheet of absorbent articles, wherein the apparatus
includes a rotatable matrix cylinder which has a plurality of
circumferentially extending rows of mutually spaced raised
plateaus; a rotatable cutting cylinder which includes
circumferentially extending knife-edges which are intended and
arranged to touch respective plateaus on the matrix cylinder, so as
to intermittently cut the web as it moves through a nip defined
between the knife-edges and the plateaus; and a rotatable press
cylinder which is mounted downstream of the cutting cylinder and
which includes circumferentially extending ribs which are
configured and arranged to engage in circumferentially extending
grooves in the machine direction of the web, located between the
rows of plateaus on the matrix cylinder so as to form in the web
recesses in the machine direction of the web, which have holes
orientated only in a plane which lies generally perpendicular to
the plane of the web.
2. Apparatus according to claim 1, wherein the raised plateaus are
formed on the tops of generally cog-shaped pegs.
3. Apparatus according to claim 2, wherein the plateaus are formed
by a ridge-shaped formation along one side edge of a peripheral
surface of the pegs.
4. Apparatus according to claim 3, wherein one side of each peg has
a convex curved shape when seen in an axial cross-section through
the matrix cylinder.
5. Apparatus according to claim 4, wherein the other side of each
peg is orientated generally radially.
6. Apparatus according to claim 1, wherein the plateaus have the
form of raised portions on circumferentially extending ribs on the
matrix cylinder.
7. Apparatus according to claim 6, wherein both sides of each rib
are orientated generally radially, seen in an axial cross-section
through the matrix cylinder.
8. Apparatus according to claim 6, wherein one side of each rib has
a convex curved shape, seen in an axial cross-section through the
matrix cylinder.
9. Apparatus according to claim 6, wherein the circumferentially
extending ribs having raised portions include a plurality of
interruptions which are mutually separated circumferentially and
which have the form of hollows, thereby forming between two
mutually adjacent hollows in the circumferential direction a
plateau row sector which includes a plurality of raised
portions.
10. Apparatus according to claim 2, wherein the cutting cylinder
has continuously circular knife-edges whose number is twice that of
the number of rows of plateaus on the matrix cylinder, and wherein
each knife-edge generally touches one side-edge part of each
plateau.
11. Apparatus according to claim 3, wherein the cutting cylinder
has continuously circular knife-edges whose number corresponds to
the number of rows of plateaus on the matrix cylinder.
12. Apparatus according to claim 1, wherein the number of ribs on
the press cylinder is one more than the number of rows of plateaus
on the matrix cylinder.
13. Apparatus according to claim 1, wherein the cylinders are
journalled in a common stand.
14. Apparatus according to claim 1, wherein the matrix cylinder is
fixedly journalled whereas the cutting cylinder and the press
cylinder are journalled so as to enable said cylinders to be
adjusted radially in relation to the matrix-cylinder in the stand.
Description
The present invention relates to a method for perforating a web of
material intended for use as a casing sheet in the manufacture of
absorbent articles, particularly a casing sheet which is intended
to lie proximal to the wearer when using the articles, for instance
sanitary napkins, diapers and like articles.
The inner perforated casing sheet of absorbent articles normally
includes a liquid-impermeable material, such ;as plastic film,
wherein the holes formed by the perforations are present in very
large numbers so as to enable liquid, or fluid, to flow
satisfactorily into the absorbent body of the article that lies
inwardly of the casing sheet.
In the case of outer casing sheets of this kind it is also
desirable to obtain a relatively small area of contact of the
casing sheet with the wearer's body, so as to produce an inner
casing sheet which will be felt to be more airy, drier and less
plastic-like by the wearer. This is achieved by forming recesses in
the web from which the casing sheet is produced, wherein the holes
are preferably orientated in planes which lie generally
perpendicular to the plane of the outer sheet. Providing that the
casing sheet is comprised of opaque material, this orientation of
the holes will also afford the advantage that the body liquid
absorbed by the absorption body will be less visible.
SE-B-44 9 298 (corresponding to U.S. Pat. No. 4,626,254) describes
and illustrates an inner casing sheet for absorbent articles in
which perforated recesses are formed in the casing sheet, wherein
the recesses include openings or holes which are orientated in
planes that lie generally perpendicular to the plane of the
sheet.
These recesses which include holes that lie perpendicular to the
plane of the sheet have been formed with the aid of vacuum-forming
against a rotating, hollow matrix cylinder, wherein the plastic
film is pressed into hollows in the matrix cylinder by the action
of hot air and sub-pressure. However, it has been found difficult
to obtain controlled and uniform shaping and orientation of the
recesses and the holes formed therein simultaneously with the
shaping process when practicing the aforesaid method.
Consequently, one object of the present invention is to provide a
method for perforating a casing sheet web which will enable the
recesses and the holes provided therein to be controlled and
forcibly given a more well-defined shape.
This object is achieved with a method according to the invention by
first making a large number of discrete cuts in the web as the web
is advanced through the nip defined between raised plateaus on a
matrix cylinder and knife-edges on a cutting cylinder, and
thereafter deforming the web transversely to its plane at parts
bordering on each cut, with the aid of a press cylinder which
presses the web into hollows in the matrix cylinder such as to
create perforated recesses in the web.
The invention also relates to apparatus for carrying out the
method, said apparatus being characterized in that it includes a
matrix cylinder which has a large number of circumferentially
extending rows of mutually separated, raised plateaus, a cutting
cylinder which has circumferentially extending knife-edges which
are intended to generally touch respective plateaus on the matrix
cylinder so as to cut intermittently, the web advanced through the
nip defined by the knife-edges and the plateaus, and a press
cylinder which is mounted downstream of the cutting cylinder and
which has circumferentially extending ribs which are configured to
engage in circumferentially extending grooves between rows of
plateaus on the matrix cylinder, such as to form in the web
recesses which include holes that are orientated in a plane which
lies generally perpendicular to the plane of the web.
The present invention also relates to a perforated outer casing
sheet, particularly the inner casing sheet of absorbent articles,
such as sanitary napkin, diapers or like articles, wherein the
casing sheet includes a large number of perforated recesses in
which the holes or perforations are orientated in a plane which
lies generally perpendicular to the plane of the casing sheet.
According to the invention, the recesses are mainly characterized
in that they are formed by mutually adjacent, elongated
channel-like grooves.. This enables the whole area per unit of
surface area to be increased and the contact area with the wearer's
body to be reduced, while enabling the elastic properties of the
outer casing sheet to be influenced transversely to the grooves as
desired.
Suitable embodiments of the inventive method and the inventive
apparatus and also further features thereof will be described in
more detail below with reference to the accompanying drawings in
which
FIG. 1 is a schematic perspective view of inventive apparatus for
perforating a web of material, and also shows fragmentary partially
enlarged views of the main components of the apparatus and of the
perforated web;
FIG. 1a is a fragmentary perspective view of alternative
positioning of the cog-like pegs on the matrix cylinder;
FIG. 2 is a fragmentary cross-sectional view which illustrates
cutting of a web in a nip defined between a matrix cylinder and a
cutting cylinder;
FIG. 3 is a fragmentary cross-sectional view which shows the
engagement between the matrix cylinder and a press cylinder,
wherein the plane of the web is displaced and perforated recesses
are formed by plastic deformation of the web across pegs on the
matrix cylinder;
FIG. 4 illustrates an alternative embodiment of the pegs; on the
matrix cylinder in engagement with ribs on the press cylinder;
FIG. 5 is a fragmentary view of a row of perforated recesses of a
"hammock-like" configuration, produced by means of the apparatus
according to the FIG. 1 embodiment;
FIG. 6 illustrates a row of perforated recesses of "eyebrow-like"
configuration, produced by means of a matrix cylinder having pegs
according to the FIG. 4 embodiment;
FIG. 7 illustrates a sector-shaped mantle part and a fragmented
part of ribs of a modified embodiment of the matrix cylinder;
FIG. 8 illustrates elongated channel-like or groove-like recesses
in the web, formed by a matrix cylinder in accordance with FIG. 7;
and
FIG. 9 illustrates elongated channel-like or groove-like recesses
in a web, formed by a matrix cylinder similar to that shown in FIG.
7 but with press ribs that have a cross-sectional shape
corresponding to the cross-sectional shape of the pegs shown in
FIG. 4.
FIG. 1 illustrates inventive apparatus, generally referenced 10,
for producing perforated recesses in a web of material 12 which is
intended to form an outer casing sheet for absorbent articles such
as sanitary napkins, diapers and like articles, and more
specifically to form the liquid-permeable inner casing sheet that
lies proximal to the wearer's body in use. The web 12 may consist,
for instance, of plastic film or may be comprised of a plastic
film/nonwoven laminate, wherein in the latter case the plastic
sheet will form the surface that is in contact with the wearer of
the article.
In principle the apparatus 10 is comprised of a matrix cylinder 14,
a cutting cylinder 16 and a press cylinder 18. These cylinders are
journalled for rotation in a stand 20 and can be adjusted in
relation to one another for adequate mutual abutment and
engagement. According to the embodiment illustrated in FIGS. 1-3,
the matrix cylinder 14 includes a large number of circumferentially
extending and axially separated rows of generally cog-like pegs 22
which have curved top surfaces that form raised plateaus 24 against
which the knife-edges 26 of the cutting cylinder 16 are intended to
abut or generally touch, so that as the web 12 is advanced through
the nip defined between matrix cylinder and cutting cylinder 14 and
16 respectively there will be formed in the longitudinal direction
of the web a large number of mutually separated cuts, as shown more
clearly in FIG. 2. In this case, the knife-edges 26 on the cutting
cylinder 16 are intended to cut the web 12 at side-edge parts of
the plateaus 24 of the pegs 22 and accordingly have twice the
number of edges 26 as the number of rows of pegs 22.
FIG. 1a illustrates a modified embodiment of the matrix cylinder
14, wherein the pegs 22 of mutually adjacent rows of pegs are
offset mutually in the peripheral or row direction, thereby
enabling the elasticity to be varied appropriately transversely to
the finished imprinted web, as desired.
The press cylinder 18 has a large number of circumferentially
extending press ribs 28 which are configured and arranged to engage
in the circumferentially extending grooves 30 located between the
rows of pegs 22 on the matrix cylinder 14. As shown in FIG. 3, the
press ribs 28 move the web 12 inwardly against the bottom of the
grooves 30 and the spaces 32 between the pegs 22, therewith
deforming the web 12 plastically on one side of each cut in the
web, such that hammock-like recesses 34 (FIGS. 1 and 5) are formed
across the pegs 22 with opposing hole openings 36 orientated
essentially in a plane which extends perpendicular to the plane of
the web 12.
FIG. 4 illustrates an alternative embodiment of the matrix pegs
22', where one side wall 38 of respective pegs has a convex curved
shape--seen in an axial cross-section through the matrix
cylinder--to form a ridge-like formation 40 on the opposite side
edge of the peg 22'. Thus, when cutting the web 12 with the aid of
a cutting cylinder of this configuration one knife-edge 26 is
omitted for each peg 22'. The recesses 34' formed in the web by
said subsequent pressing of the ribs 28 on the press cylinder 18
into the grooves 30 defined between the rows of pegs therewith
obtain an eye-brow like shape (FIG. 6) having solely one hole
opening 36 orientated generally perpendicular to the web 12.
Although a recess 34' of this configuration will result in a
smaller total hole area of the web, there is achieved, on the other
hand, much better shape stability of the recesses.
FIG. 7 illustrates part of a further embodiment of an inventive
matrix cylinder 14'. Distinct from the pegs 22, 22' of the
embodiment illustrated in FIGS. 1-4, this matrix cylinder has
circumferentially extending ribs 42 which have a configuration
corresponding to the configuration of the pegs 22 shown in FIG. 3,
when seen in an axial cross-section through the cylinder. The ribs
42 have arranged along their cylindrical mantle surfaces a
plurality of raised plateaus 24' which are mutually separated
circumferentially and which correspond to the tops of the pegs 22.
However, the mutually adjacent plateaus 24' are not separated
circumferentially by cog-like interspaces, as are the pegs 22.
Thus, those recesses that are formed on the web as the press roll
18 engages the matrix cylinder 14' obtain an elongated,
channel-like or groove-like configuration 34" with an increased
hole area and reduced user body contact surface, as shown in FIG.
8. The grooves 34" are delimited by two opposing side walls 35a in
which the holes 36 are formed, and a bottom wall 35b. The groove
configuration of the recesses 34'" shown in FIG. 9 is obtained when
the matrix ribs 42 have a cross-sectional shape corresponding to
the cross-sectional shape of the pegs 22' shown in FIG. 4. In this
case, the grooves 34'" are delimited by a side wall 34a' and a
sloping bottom wall 35b'.
The matrix cylinder 14' may have ribs which extend continuously
around the cylinder, or, as shown in FIG. 7, ribs 42 which are
broken by cog-like interruptions 44 which give each rib 42 the form
of a sector having a plurality of plateaus 24'. FIG. 7 shows one
such sector having twenty plateaus 24' and which constitutes one
tenth of the periphery of the whole matrix cylinder 14'. As a
result of the interruptions 44 in the ribs 42 there is obtained in
the perforated and imprinted web transverse web parts 46 (FIGS. 8
and 9) which are able to stabilize the material and to limit the
stretch and elasticity of the web in its transverse direction in a
suitable manner as desired.
* * * * *